The first phase of an investigation into assaults and fight clubs at Mt Eden prison has finished but it is not clear when the report will be made public.
The investigation by the chief inspector of prisons was extended by two months because of the high number of complaints from prisoners and their families.
It has looked at the circumstances of fights between prisoners, access to cellphones and the adequacy of reporting on incidents of prisoner violence.
The report has been sent to Department of Corrections chief executive Ray Smith for review.
It will also be sent to private prison operator Serco and government ministers, but a Corrections spokesperson could not give a date for its public release.
A report on the second phase of the inquiry is due at the end of November.
Corrections took over the management of Mt Eden prison from Serco in July after claims of violent attacks on prisoners and video footage of prison fight clubs being posted online.